Calling Lua function without executing script

Question

I am embedding Lua into a C/C++ application. Is there any way to call a Lua function from C/C++ without executing the entire script first?

I've tried doing this:

//call lua script from C/C++ program
luaL_loadfile(L,"hello.lua");

//call lua function from C/C++ program
lua_getglobal(L,"bar");
lua_call(L,0,0);

But it gives me this:

PANIC: unprotected error in call to Lua API (attempt to call a nil value)

I can only call bar() when I do this:

//call lua script from C/C++ program
luaL_dofile(L,"hello.lua");  //this executes the script once, which I don't like

//call lua function from C/C++ program
lua_getglobal(L,"bar");
lua_call(L,0,0);

But it gives me this:

hello
stackoverflow!!

I am wanting this:

stackoverflow!

This is my lua script:

print("hello");

function bar()
 print("stackoverflow!");
end

Since you have to run the script to get the Lua VM to see it like Etan indicated you'll have to extract out function bar() to a different file and just run that file. — greatwolf

Etan Reisner Etan Reisner · Accepted Answer · 2010-02-27T03:47:46

As was just discussed in #lua on freenode luaL_loadfile simply compiles the file into a callable chunk, at that point none of the code inside the file has run (which includes the function definitions), as such in order to get the definition of bar to execute the chunk must be called (which is what luaL_dofile does).

Calling Lua function without executing script

3 Answers